American Telephone & Telegraph Co., At&t Bell Laboratories

Curtin University of Technology

At&t Bell Laboratories

Other

Zigmantas Leonas Budrikis

Arun N Netravali

John Leslie Hullett

Mehdi Hatamian

Antonio Cantoni

Rodney C Alferness

Herwig Werner Kogelnik

Peter Steve Kubik

Robert M Newman

Vaughan William Wittorff

Guven Mercankosk

John Siliquini

David W Hagelbarger

The present invention allows routers in a digital communications network, such as the Internet, to be given the time awareness that is necessary for timely transfer of real time signals in the form of digital data packets. Timing information generated at the source of the signal is included in the packets in the form of first and second time stamps, which are used by network routers to establish dispatch deadlines by which the packets must be forwarded to ensure time-faithful reconstruction of the real time signal at the destination. The same timing information can be used at the destination to synchronize the clock for presentation of the real time signal to the source clock. The first and second time stamps (a differential time and a dispatch time) are derived by a transmitter unit () from a counter () that counts pulses from an oscillator () that most advantageously is locked to an integer multiple or a fraction of a universally available time measure. Assuming that the same time measure, or at least a very near replica, is available at routers in the network and at destinations connected to the network, the time stamps marked in the packets can be used by routers to effect scheduling for timely dispatch of the packets.

Method and apparatus for transfer of real time signals over packet networks

A method of controlling the flow of traffic in synchronous transfer mode (ATM) network ( ), which brings into possible existence a class (class II) of ATM cells. The ATM network ( ) comprises one or more ATM switches ( ) coupled by links ( ) providing communication channels between the ATM switches ( ). The method subjects the class II cells received at an input port of a particular ATM switch ( ) to control, originating within the switching element of that ATM switch. The method allows only up to a fixed number of class II cells from a particular input port to be in the switch awaiting onward transfer. Although the control is on class, it nonetheless tends to produce fairness in service among different connections.

Switching protocol providing controlled access to available asynchronous network service

Method and apparatus for managing the statistical multiplexing of data

A method of transmitting digital signals (DI) in frames which include a stuffing field between nodes (N) in a network, each node having a buffer and a local clock for producing local clock signals (CLK2). The method includes the steps of extracting clock signals (CLK1) from the digital signals (DI), writing the digital signals into a buffer at the extracted clock signal (CLK1) rate, reading the digital signals from the buffer including reading the content of the stuffing field in order to add or substrate stuffing bits therein in order to compensate for differences in frequencies between the local and extracted clock signals (CLK1, CLK2), and controlling the adding or subtracting of stuffing bits so that the length of the stuffing field is within predetermined limits.

Jitter control in digital communication links

An arrangement for butt coupling of waveguide electrooptic plates to form a crossbar switch. The arrangement includes a stack of M splitter plates, each of which routes an injected optical signal to one of N outputs, and a stack of N combiner plates, each of which routes the signal of a selected one of M inputs to a common output. The stack of splitter plates is rotated with respect to the stack of combiner plates and the output signal ports of the splitter plates are coupled to the input signal ports of the combiner plates, so that each output of an splitter plate is connected to a different combiner plate. Within each splitter plate there is a fan-out network of waveguide electrooptic couplers and each coupler, under electric control, routes signals from one input to either one of two outputs. With j levels of such interconnected couplers 2.sup.j output are developed. The combiner plates have an identical architecture but with a signal flow in the reverse direction. Butt coupling of the splitter and combiner plates is achieved by employing splitter and combiner plates of a different crystal cut, by interposing polarization rotation means between two stacks, or by including polarization rotation means within the splitter plates, the combiner plates or both.

Optical interconnect arrangement

A method and apparatus that employ precomputed line profiles to draw lines on a raster scan terminal with mostly horizontal or vertical 'brush strokes' that develop the desired line profiles. The precomputed line profiles relate mostly to the slope of the drawn lines and to the position of the drawn lines between adjacent pixels on the raster scan terminal in the direction of the 'brush strokes'. A relatively small number of precomputed values is required, permitting the apparatus to operate at the low resolution of the raster scan and be driven advantageously by a look-up table. This results in a very fast operation of the system while leading to pleasing results. The method also takes into account corners and end-of-line conditions to avoid very abrupt and unnatural looking end points.

Method and apparatus for drawing antialiased lines and polygons

The generation of individual moments of an image is advantageously achieved by generating a plurality of filtered signals in which each filtered signal is a linear combination of individual ones of the desired moments rather than the actual moment themselves. These filtered signals are obtained by passing the image signals through a series of single pole digital filters arranged as a matrix of filters. Each moment is formed at the end of an image frame by dematrixing the filtered signals. An illustrative embodiment uses repeating circuit patterns so that it can be easily integrated onto a circuit chip.

Moment generator

A light pen which includes a transparent rod at its pointing end through which light is directed to a photodetector that is fixedly positioned within the light pen. The rod is spring loaded and axially slidable in response to applied pressure, resulting in different light intensities being applied to the photodetector and further resulting in an output voltage generated by the photodetector that is directly related to the applied pressure.

Pressure-sensitive light pen

This disclosure relates to the instant method and system for controlling the interconnecting of a plurality of local communications networks. A source station and a destination station may respectively be adapted to be coupled to at least one communications channel of a communications path, which path includes a plurality of channels, each channel being assignable to at least one of a plurality of local data networks. The respective stations are adapted to determine the home network of the other respective stations with which the respective stations may communicate. Broadly, a source station, which has a message to transmit to a destination station, determines the home network of the destination and couples a first source receiver and a source transmitter to the home network of the destination for transmitting a packet from the source to the destination. A first packet may be transmitted when the source station acquires access to an idle channel of the destination home network. Further packets may be transmitted, not on the destination home network, but rather on the source home network. The source transmitter may be decoupled from the destination home network (if already so coupled) and may be coupled to the source home network for such further packet transmission.

Growing community of inventors

Dalkeith, Australia

Zigmantas Leonas Budrikis